1. Field of the Invention
This invention relates to general purpose bombs. The general purpose bomb can be used to great effect against a variety of targets, depending upon its capabilities, and the nature of the target.
2. Discussion of the Prior Art
A principal use is against hard targets such as hardened aircraft shelters, bridge piers, aircraft runways, and the like. Against such hard targets the general purpose bomb is generally ineffective unless the bomb is able to penetrate into the target prior to detonation, so that the blast and heave effects on the target are maximised.
However, in modern warfare certain targets are extremely well protected. Hardened aircraft shelters may be protected by one or more meters of reinforced concrete which may be covered by a layer of soil or sand. Aircraft runways may be several meters thick. Tactical bunkers may be protected by several meters of reinforced concrete with mounded earth providing further protection.
Considerable effort has been devoted to the development of high penetration bombs capable of penetrating modern hard targets. These efforts have largely been directed towards the development of bombs designed to penetrate the target by virtue of their kinetic energy. This has led to long, thin designs having thick cases, which necessitates a reduction in the proportion of high explosive to about 20-25% of all-up weight. The terminal effect of the bomb is correspondingly reduced. Its penetration into the target is also critically dependent upon its velocity of impact, which in practice needs to be approaching Mach 1.0. This increases the difficulty of delivery.
It has been proposed in U.S. Pat. No. 4,488,487 to assist the penetration of a bomb dependent primarily on its kinetic energy, by the addition of some kind of small primary charge in the nose of the bomb. Such a charge might be a shaped charge. Its purpose is to condition the target material in the immediate impact area, so as to enable the bomb casing to penetrate slightly into the target, thus providing a toe-hold to counteract possible ricochet, especially at relatively low angles of incidence. The effectiveness of such designs has been limited, in that the small primary charges used have not been capable of conditioning a sufficient target volume to increase the initial penetration significantly.
In West German Patent No 2629280 there is disclosed a small tandem-charge munition, comprising a shaped-charge primary penetrator in a heavy metal casing, and a secondary charge. The overall caliber of the munition is 100 mm, and the secondary charge has a diameter of about one third of this. It is recognised that when the primary charge is detonated, it would have the effect of disrupting the secondary charge, and also that the rearward blast from the primary would cause the secondary charge to be driven away from the target.
Various special measures are described in order to counteract these effects, so that the secondary charge can be effectively emplaced within the target. These measures include the complication of a propelling charge and mechanism to ignite this charge at the correct instant to drive the secondary charge forward, against the blast from the primary charge.
West German Patent No 2829002 (to the same patentee) discloses another form of small-scale tandem warhead having primary and secondary charges of a comparable caliber. In this case it has been found necessary to provide mechanism for moving the primary and secondary shaped charge warheads longitudinally apart immediately prior to impact with the target in order to reduce the disruption of the secondary charge to an acceptable level.